#include <bits/stdc++.h>
#include "highway.h"
using namespace std;
typedef long long ll;
int edgeCnt;
vector<vector<pair<int, int>>> adj;
vector<pair<int, pair<int, int>>> edges;
void find_distances(int index, int last, int dist)
{
dist += 1;
for (auto node : adj[index])
{
if (node.first == last) continue;
edges.push_back({dist, node});
find_distances(node.first, index, dist);
}
}
int find_S(ll dist)
{
// Sort all edges by bfs_distance
// from arbitrary root node (0)
find_distances(0, 0, 0);
sort(edges.begin(), edges.end());
int l = 0, r = edgeCnt - 1;
while (l < r)
{
int c = (l + r + 1) / 2;
vector<int> w(edgeCnt);
for (int i = c; i <= r; i++)
w[edges[i].second.second] = 1;
ll cur_dist = ask(w);
if (cur_dist == dist)
r = c - 1;
else
l = c;
}
return edges[l].second.first;
}
int bfs_dist;
vector<pair<int, int>> sus_edges;
void find_sus_edges(int index, int last, int dist)
{
dist += 1;
for (auto node : adj[index])
{
if (node.first == last) continue;
if (dist == bfs_dist)
sus_edges.push_back(node);
else
find_sus_edges(node.first, index, dist);
}
}
int find_T(int root, ll dist)
{
find_sus_edges(root, root, 0);
int l = 0, r = sus_edges.size() - 1;
while (l < r)
{
int c = (l + r + 1) / 2;
vector<int> w(edgeCnt);
for (int i = c; i <= r; i++)
w[sus_edges[i].second] = 1;
ll cur_dist = ask(w);
if (cur_dist == dist)
r = c - 1;
else
l = c;
}
return sus_edges[l].first;
}
void find_pair(int N, vector<int> U, vector<int> V, int A, int B)
{
edgeCnt = U.size();
adj = vector<vector<pair<int, int>>>(N);
for (int i = 0; i < edgeCnt; i++)
{
adj[U[i]].push_back({V[i], i});
adj[V[i]].push_back({U[i], i});
}
ll dist = ask(vector<int>(edgeCnt));
bfs_dist = dist / A;
int S = find_S(dist);
int T = find_T(S, dist);
//cerr << "Guess: S = " << S << ", T = " << T << '\n';
answer(S, T);
}
